incidence - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 2 CK Forum

USMLE Step 2 CK Forum USMLE Step 2 CK Discussion Forum: Let's talk about anything related to USMLE Step 2 CK exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 08-05-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,867
Threads: 149
Thanked 2,086 Times in 1,046 Posts
Reputation: 2106
Default incidence

In a city with a population of 1,000,000, 10,000 individuals have HIV disease. There are 1000 new cases of HIV
disease and 200 deaths each year from the disease. There are 2500 deaths per year from all causes. Assuming
no net emigration from or immigration to the city, the incidence of HIV disease in this city is given by which of the
following?


A. 200/1,000,000

B. 800/1,000,000

C. 1000/1,000,000

D. 2500/1,000,000

E. 10,000/1,000,000
Reply With Quote Quick reply to this message



  #2  
Old 08-05-2012
USMLE Forums Scout
 
Steps History: 1+CK+CS+3
Posts: 93
Threads: 21
Thanked 37 Times in 16 Posts
Reputation: 47
Default

i would say C
Reply With Quote Quick reply to this message
  #3  
Old 08-05-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 1,867
Threads: 149
Thanked 2,086 Times in 1,046 Posts
Reputation: 2106
Default

Explanation:

The correct answer is C. The incidence of a disease is given by the number of new cases in a given period
divided by the total population. In this case, this is equal to 1000/1,000,000.

The disease-specific mortality rate is the number of deaths per year from a specific disease divided by the
population; in this case, 200/1,000,000 (choice A).

The rate of increase of a disease is given by the number of new cases per year, minus the number of deaths
(or cures) per year, divided by the total population. Since there is yet no cure for HIV disease, the number of
cures is 0. In this case, the rate of increase is (1000-200)/1,000,000 = 800/1,000,000 (choice B).

The crude mortality rate is given by the number of deaths from all causes, divided by the population; in this
case, 2500/1,000,000 (choice D).

The prevalence of a disease is defined as the number of cases of the disease at a given time divided by the
total population. In this case, it would be 10,000/1,000,000 (choice E).
Reply With Quote Quick reply to this message
  #4  
Old 08-08-2012
USMLE Forums Scout
 
Steps History: CS Only
Posts: 18
Threads: 8
Thanked 12 Times in 1 Post
Reputation: 22
Default

Quote:
Originally Posted by Novobiocin View Post
In a city with a population of 1,000,000, 10,000 individuals have HIV disease. There are 1000 new cases of HIV
disease and 200 deaths each year from the disease. There are 2500 deaths per year from all causes. Assuming
no net emigration from or immigration to the city, the incidence of HIV disease in this city is given by which of the
following?


A. 200/1,000,000

B. 800/1,000,000

C. 1000/1,000,000

D. 2500/1,000,000

E. 10,000/1,000,000


i have a doubt . To calculate incidence , do we need to include people who are dead or already have the disease !! I mean isnt incidence New cases/Potential cases.

like denominator here should ve been according to this concept ,

1,00,000 -[(10,000 + 2500)] = 87500

so incidence = 1000/87500
Reply With Quote Quick reply to this message
  #5  
Old 08-08-2012
USMLE Forums Master
 
Steps History: 1+CK+CS
Posts: 590
Threads: 31
Thanked 1,227 Times in 410 Posts
Reputation: 1251
Default

Quote:
Originally Posted by Shankar View Post
i have a doubt . To calculate incidence , do we need to include people who are dead or already have the disease !! I mean isnt incidence New cases/Potential cases.

like denominator here should ve been according to this concept ,

1,00,000 -[(10,000 + 2500)] = 87500

so incidence = 1000/87500
Even if you take out everyone who already has it and the people who die, you are still left with an incidence of 1,000/987,500. That equals 987.5/1,000,000, which is much closer to 1,000/1,000,000 than any of the other answers. So C is still the best answer...
Reply With Quote Quick reply to this message



Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Incidence Calculation; What's the denominator? sonu.agarwall USMLE Step 2 CK Forum 5 08-01-2012 06:24 AM
Calculating the Incidence Rate! hypermedic USMLE Step 1 Forum 2 07-13-2012 02:56 PM
Reducing incidence of a cancer..... anomali USMLE Step 1 Forum 4 06-14-2012 11:52 AM
Epidemiology: How to calculate Incidence? mycoplasma USMLE Step 1 Forum 3 05-17-2012 12:11 PM
the incidence of HIV disease USMLE-Syndrome USMLE Step 1 Forum 2 02-08-2012 01:02 AM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)